Cell culture and expansion is a very important step in cell therapy and mesenchymal stem cells (MSCs) represent the second most selected stem cell group (after haematopoietic stem cells) in the adult stem cell market today.
A recent upsurge in the use of primary and stem cells (e.g. MSCs) for cell based therapy has created a growing need for cell culture systems that can be used to expand these cell types. Typically, MSCs are grown in monolayer T-flask cultures, which is labor intensive and space requiring if large amount of cells are to be produced. There is one article describing successful culture of porcine bone-marrow derived MSCs on microcarriers in spinner flasks (Frauenschuh, S., E. Reichmann, et al. (2007). “A Microcarrier-Based Cultivation System for Expansion of Primary Mesenchymal Stem Cells.” Biotechnol Prog 23(1): 187-193.) However, this is not a disposable system and the shear forces from the mechanical mixing may damage the cells.
Previous published results have shown that it is possible to expand various types of cells (e.g. Vero cells and MDCK cells) on microcarriers in the Wave Bioreactor (Genzel, Y., R. M. Olmer, et al. (2006). “Wave microcarrier cultivation of MDCK cells for influenza virus production in serum containing and serum-free media.” Vaccine 24(35-36): 6074-87.). The applications for these cultures lie in the vaccine production area, where there still is a need for improved productivity for cultivation methods with better scalability. The vaccine protocols cannot be fully applied to primary cell cultivation since they differ from cancer cell lines in several ways. For instance, MSCs and other stem cells are more sensitive and proliferative properties are limited as they lose their multilineage capacity after certain number of passages.
US 2007-0264713 relates to a method for proliferating stem cells on microcarriers. The stem cells, the microcarriers as well as culture medium are introduced into a container which could be a spinner flask or a bioreactor. An intermittent agitation technique is used in the method, wherein the medium is moved between 10 and 100 minutes and not moved between 10 and 60 minutes. The method is said to provide large yields of stem cells.
However, there is still a need of a new method suitable for expanding adherent cells, such as primary cells and stem cells, in bioreactors, for clinical scale production.